Survival bias: what is this logical fallacy?

Let's see what survival bias is and how it leads us to wrong conclusions.

Sometimes we draw overly optimistic conclusions about a given issue and we do so through survival bias. through survivorship bias.

Let's discover the implications of this logical error and some of the most common scenarios in which we can observe this phenomenon, as we will see that it is not a bias that is more prevalent in a particular area but can occur in a variety of situations.

What is survival bias?

Survivor bias or survivor bias is a type of argumentation failure. a type of flaw in logical argumentation that leads us to look only at items that have passed a particular selectionThe limitation of the study is that it is not possible to ignore the existence of all those elements, which may sometimes be the majority or have interesting attributes that were forgotten. This limitation may cause the observer to completely ignore the mere existence of all these elements, which may sometimes be the majority or have interesting attributes that were lost in oblivion.

This is not the only error. In addition, the survival bias can sometimes lead us to fall into unjustified optimism. The fact is that evaluating a given situation only takes into account those people or elements that have passed the evaluation barrier or the selection process in question. Counting only with the characteristics or testimonies of those and not of the total number of participants can be a mistake.

In order to better understand what the survival bias is all about let's try to visualize it with an example. Suppose we organize a car race and when it ends, we take for granted that the first three are, without a doubt, the best cars there are to compete. But a multitude of situations could have occurred that have caused the rest of the cars to be left behind.

For example, there may have been an accident that has knocked out top cars. The tires chosen by some of the participants may not have been optimal to take advantage of the characteristics of the car and the circuit. They may even have been worse drivers and failed to exploit the potential of the car, which could even have been better than that of the winners.

These are just some of the options whereby we could easily be falling into survival bias, thinking that the cars at the top are automatically the best. To arrive at such a statement we need to inquire in depth about the characteristics, not only of them, but also of all the other participants. Only then will we be in a position to to draw conclusions with propriety.

Areas in which this logical error is most prevalent

Survival bias is a phenomenon that can occur in almost any field. This is why we are going to make a compilation of some of them in order to understand the magnitude of this logical fallacy and the dangers it entails if we are not aware of its effects.

1. At the economic level

Probably one of the most important scenarios to take into account the possible appearance of survival bias is the economic or financial one, since the consequences can be dire. In this case, such a bias would refer to the exclusion in any type of report of all those companies or other types of organizations that have been closed down..

Therefore, information on a multitude of companies that, having gone bankrupt, would not be included in certain statistics and indicators, which would be composed only of those that are still standing, would be left out of focus. This would be one of the cases in which a large amount of information, sometimes very important, would be ignored.

2. At the historical level

We have all heard the statement that history is written by the victors. In a way, this is a way of expressing the effect of survival bias on historical events. In these cases, for example, it is usually the winning side of the conflict that is responsible for shaping the narrative about the war they have fought, its origins and its consequences..

Sometimes such an account is reasonably objective, but in others it is a real puzzle for historians, who have to study the documents in great detail to ensure that the events occurred as that party maintains. Assuming that there are still documents to investigate, it is also possible to eliminate evidence that is of no interest, about a past that "never" happened.

3. In the professional field

We cannot forget that survival bias also applies to individuals themselves and of course to their careers. For every great soccer player, famous actor, renowned writer or reputed manager, there are thousands who, having similar characteristics, failed on the same path.

In this case, to consider only the qualities of those who achieved success as an infallible formula would be a mistake.We would be leaving out of focus a multitude of variables, many of them uncontrollable or random, which surely had a great deal to say in the failure of the rest.

4. In the quality of goods

Sometimes we have the feeling that objects, clothes or machinery created today are deliberately designed to last a certain time. They call it planned obsolescence. The argument is that there are items of the same genre but created long ago that still maintain their qualities.

There would be a case of survival bias here, as we would be focusing on the specific example and ignoring the vast number of items of the same type that never made it to the present day. If we were to take into account the total number of objects created in a given era and could establish statistics on those that have proven their durability and those that have not, perhaps our opinion would change.

We would probably realize that in reality, only those products designed with very specific characteristics have lasted longer than usual. and on the contrary, there have been many that have not been able to resist the passage of time as well as those minority cases.

5. Regarding architecture

Surely the reader will have the impression, well founded, that ancient buildings tend to be much more beautiful than modern ones. Does this mean that absolutely all the constructions that were made in past times were majestic and also tremendously resistant? Not at all. That would be, without a doubt, to fall into survival bias.

How then can we explain that all (or almost all) of the old buildings that remain in cities are noticeably more beautiful than the newer ones? Due to the constant renovation processes that cities undergo every few decades. This means that most buildings have an expiration date, except for those that are especially noteworthy due to their characteristics.

Therefore, these usually become part of the heritage and the aim is to restore them whenever possible instead of tearing them down and replacing them with others. This is the origin of the survival bias, since it gives rise to the idea that only old buildings survive, without taking into account that for every one that has reached our time, there are hundreds that have been reduced to rubble.

6. In war strategies

One of the strategies that the U.S. Army carried out during World War II was to study the bullet impacts received by its bombers during air battles, in order to protect especially the areas where most bullets were observed. It seemed a brilliant strategy, but it was overlooking a key factor: all the aircraft shot down in combat.

Not being able to study the destroyed aircraft made it impossible to verify where precisely those that suffered the most severe damage were shot down. This is therefore a clear case of survivor bias.

7. The seven lives of cats

Who does not know the popular saying that cats have seven lives? One of the proofs often given to support such a claim is that cats usually survive falls from great heights. How do you know this? Because veterinarians usually treat cats that have suffered injuries from a fall from several stories.

But this is another case of survivorship bias, because we are assessing only the cases of cats that survive falls, leaving aside all the cases of cats that, unfortunately, are not so lucky and die from the consequences of falling into the void. It is likely that the number of the latter is higher, but being obviated from the statistics, we continue to think that cats have seven lives.

Bibliographical references:

• Brown, S.J., Goetzmann, W., Ibbotson, R.G., Ross, S.A. (1992). Survivorship bias in performance studies. The Review of Financial Studies.
• Mangel, M., Samaniego, F. (1984). Abraham Wald's work on aircraft survivability. Journal of the American Statistical Association.
• Shermer, M. (2014). How the Survivor Bias Distorts Reality. Scientific American.
• Whitney, W.O., Mehlhaff, C.J. (1987). High-rise syndrome in cats. Journal of the American Veterinary Medical Association.